The present invention relates to a method for connecting elements of optical communication technology either one to another or to releasable plug connections wherein the elements are first connected to weldable adjustment members, the adjustment members are then displaced relative to one another with the coupling faces lying against one another without play until the desired adjusted position is reached, and subsequently the adjusted members are welded to one another in the region of the separating seam which is formed by the edges of the coupling faces. The invention is also directed to a releasable plug connection and to an optical transmitter module connected to an optical waveguide.
In the manufacture of optical transmitter modules, the desired coupling position must be provided between a laser diode and a coupling-in optics allocated to a light waveguide. This coupling position guarantees an optimum transmission of the light emitting by the laser diode into the light waveguide. In the manufacture of plug parts for releasable connections of light waveguides, a coupling position must be produced between a plug cylinder and an optical fiber and this coupling position guarantees that the core of the optical fiber is aligned exactly centrally relative to the outside circumference of the plug cylinder and thus only optimum coupling losses will occur in the finished plug connection. In both cases, the adjustment of the desired coupling position requires dimension precisions, which lie in the sub-micrometer range whereby the adjusted coupling position must remain positionably stable during the connection of the respective element and thereafter. In addition, the long-term stability in a time period of 10.sup.5 hours and a climate stability range which will be specified as 70% relative humidity at a temperature of 40.degree. C. and with temperature fluctuations in the range of between -10.degree. C. and 75.degree. C. are demanded for the fixed coupling position. Gluing methods and soldering methods are employed for fixing the coupled position or, respectively, for connecting the respective elements in the coupling position but the demands made can only be conditionally met with these gluing and soldering methods. In addition, adhesives have the disadvantage that they shrink greatly, that they have a high coefficient of thermal expansion and that they also react in an extreme sensitive way to humidity and heat. Solder connections, which creates high thermal stress of the element during the soldering process, also tend to creep easily under mechanical stresses.
A method for manufacturing the plug parts for releasable plug connections of light waveguides wherein the optical fibers are first secured in a central bore of a hollow cylindrical adjustment member are disclosed in German OS No. 2,704,140. In this method, the adjustment member is provided with a cylindrical collar whose back annular surface forms a coupling surface set back relative to an end face of the optical fiber. The coupling surface has a second coupling surface allocated to it and the second surface is formed by an end face of a plug cylinder, which has a structure of a hollow cylinder. The adjustment member is then inserted into the plug cylinder so that the two coupling surfaces lie against one another and both parts can be dislocated relative to one another until the desired adjusted position, which has the core of the optical fiber aligned precisely and centrally relative to the outside circumference of the plug, is obtained. After this adjusted position is reached, the adjustment member is then fixed in the plug cylinder whereby this fixing is undertaken, for example, by gluing, soldering or welding. For finishing a complete plug connection, two plug parts, which may be manufactured in such a fashion, are inserted into a common sleeve and pressure against one another until the end faces of the optical fibers lie against one another.
A method of manufacturing optical transmitter modules in which a light waveguide and coupling optics are first fixed in a housing is disclosed in an Abstract of Japanese Patent application No. 57 118 212, which appeared in "Patents Abstracts of Japan", Vol. 6, No. 212, Oct. 26, 1982. As disclosed, a semiconductor diode is secured in an annular mount. The housing and the mount are then shifted relative to one another in an axial direction of the light waveguide and in two directions perpendicular thereto until the desired adjusted position with an optimum of light transmission is reached. An axially displaceable welding ring is disposed on a continuation of the housing and is then moved until it is seated against the mount. To fix the adjusted position, the ring is welded both to the mount as well as to the housing. The two welds respectively proceed over the entire circumference of the ring and are produced by means of a laser beam welding process.
When joining elements of optical communication technology to one another or to elements of releasable connections, a fixing or welding of the parts at an established adjusted position by laser beam welding has the advantage that the thermal load on the parts to be connected is low and that the fixing is long-term stable and climate-resistant. On the other hand, a welding warp, which prevents a fixing with a dimensional precision in the sub-micrometer range, will occur during this welding operation.